Engine starter drive



Jgme 30, 1953 n. L MILLER I 2,643,548

ENGINE STARTER DRIVE Filed March 14, 1951 i 914 1 5666 7&2 sa

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i? IN1/wrox z8 zozo@ @ma/OCM WITNESS atenied June 30, 1953 ENGINE STARTER DRIVE Donald L. Miller, Horseheads, N. Y., assignor to Bendix Aviation Corporation,

Delaware a corporation of Application March 14, 1951, Serial No. 215,410

9 claims. (c1. 'x4-7) The present invention relates to engine starter gearing and more particularly to that form of automatically engaging gearing which includes means for opposing undesired disengagements of the drive.

The trend of development of internal combustion engines, and more particularly automotive engines, over the past several years, has been toward higherv and higher compression ratios, and lighter moving parts. Both these factors tend to aggravate the difficulty of maintaining meshing engagement of the conventional forms f starter drives as the engine rotates past the compression points and is momentarily accelerated by sporadic explosions in one or more of the cylinders.

Various forms of so called anti-kickout drives have been developed to cope with this situation, but those which have proved efficacious in positively maintaining the gearing in mesh until the engine is reliably selfoperative have generally relied on added features which tend to make the device complicated and expensive.

It has been found in many cases, however, that such complete and positive maintenance of the cranking connection is not required for satisfactory cranking operation, and a drive which will not be instantly demeshed by one or more vigorous explosions, such as that disclosed, for instance, in the patent to Kearney 2,163,841 is acceptable for most installations. Such slowdemeshing drives as heretofore constructed, however, have been somewhat noisy and subject to unnecessary wear due to the dragging of the pinion teeth on the engine gear teeth as they move out of mesh. Another difficulty which has been encountered is in connection with the use of the dental types of overrunning clutch. This type is preferred because of its many structural advantages, but they are most satisfactory when the clutch members are forced tightly together during the transmission of torque therebetween. ln such arrangements as heretofore constructed, however, this clamping action can be released only byA backward movement of the traversing means which latter may thus be swung 4back by a powerful explosion of the engine with sufficient force to cause demeshing of the pinion. This action has heretofore been reliably controlled only by some form of latching device such as It is another object to provide such a device including a dental type of overrunning clutch in which the clutch teeth are free to disengage without requiring any withdrawing movement of the traversing means.

It is another object to provide such a device in which the final demeshing movement of the pinion is accelerated to prevent tooth interference with the engine gear.

It is another object to provide such a device in which the accelerating means also serves to prevent the pinion from drifting away from its idle position.

Further objects and advantages will be appar- Vent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation, partly broken away and in section of a preferred embodiment of the invention showing the parts in normal or idle position;

shown for instance in the patent to Buxton It is an object of the present invention to provide a `slow demeshing starter drive which is simple in construction and quiet in operation.

Fig. 2 is a similar view showing the parts in cranking position;

Fig. 3 is a similar view showing the rparts in the position assumed when the engine fires and causes the pinion to over-run the drive;

Fig. 4 is a similar view showing the parts in their positions shortly before the time when the pinion disengages itself from the engine gear;

Fig. 5 is a detail of the structure illustrated in Fig. 4, showing an alternative form of clutch controlling spring member.

In Fig. 1 of the drawing there is illustrated a power shaft I on which a pinion 2 is slidable for movement into and out of mesh with a gear 3 of the engine to be started. A screw shaft is lixedly mounted on the power shaft as by a means of a cross pin 5 which also serves to anchor a back stop collar 6 on the screw shaft. A control nut l is threaded on the screw shaft and normally maintained in idle position against the stopcollar as shown in Fig. 1 by an anti-drift detent 8.

A ycoupling member 9 is' located between the control nut l and the pinion 2 and is maintained in alinement with the control nut by a sleeve li which is slidably mounted on the adjacent ends of the control nut and coupling member. Sleeve Il is yieldably held against a flange l2 on the control nut by a light spring i3, the opposite end of which bears against a flange i4 on the coupling member 9. The control nut 'l is provided with coupling teeth 20 having inclined driving surfaces adapted to cooperate with similar surfaces of teeth 20a formed on the coupling meinber 9. A flange member I5 is xedly mounted on the end of the pinion 2 in any suitable manner as indicated at I6, and is provided with overrunning clutch teeth I 'l adapted to cooperate with similar teeth I8 formed on the adjacent end of the coupling member.

A heavy compression spring I9, here shown in the form of a plurality of spring disks is mounted on the control nut l and maintained under initial compression against the ange I2 by means of an annular thrust plate 2I located on the control nut by a split lock ring 22. A barrelmeinber 23, arranged to surround the coupling and clutch members, is providedatone'end 'with an inturned flange 24 bearing against the flange member I5 of the pinion 2, and at itsr other end receives the thrust plate 2I which is retained in the barrel by a split lock ring 25. The length of the barrel 23 is suchfas to permit the coupling member 9 to be partially disengaged from the control nut I as shown in Fig. 1, but to cause any further disengaging movement 'to compress the heavy spring I9 which is designed to resist disengagement and slippage of the connection between the control nut and coupling member except under conditions of excessive load;

In operation, starting with the parts in the positions illustrated in Fig. l, rotation of the power shaft I in the direction of the arrow causes the control nut 'I to be traversed to the right, carrying with it the coupling member 9, pinion'2 and barrel 23, until the pinion is meshed with the engine gear 3, whereupon the threads ofthe control nut engage the ends v26 of the threads of the screw shaft so that the control nut is forced to rotate with the power shaft. This rotation is transmitted through the inclined teeth20, 20a of the control nut and coupling membenforcing the coupling member againstthe ange I5 of the pinion so as to tightly clamp togetherthe overrunning clutch teeth II, I8 and thereby transmit rotation to the pinion to crank the engine. If the initial resistance of the engine to rotation causes excessive stresses to be built up in the drive, the inclined coupling teeth '20, 20a Will produce sufiicient longitudinal pressure to compress the drive spring I9 and permit the coupling teeth to slip by each other until the excessive torque is dissipated.

When the engine re's, the 'acceleration of the pinion 2 causes it to overrunthe coupling member 9, which latter moves back slightly "against the light compression spring I3 to l'allow the clutch teeth I'I, I8 to disengage as vshown in Fig.3.

It is important to note that the structure here disclosed, the clamping together of the overrunning clutch teeth II, I 8'during cranking is secured by the action of the inclined teeth 20, 20a of the control nut and coupling 'member and not by the screw-jack action of the screw shaft and control -nut as has been the previous practice. This innovation permits the pinion to overrun freely without transmitting the initial spinning impulse to the control nut which is characteristic of the drives in which the screw-jackaction of the control nut is used to clampthe overrunning clutch members together during the cranking operation, and which impulse, as 'above pointed out, may cause premature demeshing in case of a false start unless some form' of restraining latch or detent is incorporatedin the drive.

If the engine should'not remain self-operative. the pinion slows downto the speed ofthe motor 4 shaft, the spring I3 then reengages the overrunning clutch teeth and cranking is resumed.

When the engine starts, the overrunning pinion transmits a small amount of torque back to the control nut by reason of the rubbing action of the overrunning clutch teeth caused by the spring I3. This will gradually accelerate the control nut lto "a higher speed than the screw shaft and thus cause rthe nut to traverse the parts back to their idle positions.

Fig. 4 of the drawing illustrates the operation of means vfor accelerating the demeshing movement when the pinion disengages the ring gear in order to assistin securing smooth and quiet demeshing action.V As there shown a sleeve 3I is xedly attached in any suitable manner to the screwshaft `4 and is provided with a terminal flange 32 against which a slidable ring 33 is'n'ormally maintained by a compression spring 34. The flange 32 is "so located, that as shown in this ligure, the ring 33 is engaged by an internal flange 35 on the coupling member just prior to the time'when the'pi'ni'on 2 moves out of engagement'with the engine gear 3.

Further movement of the parts ina demesh- Ying direction therefore causes compression of the spring 34 which increases'the pressure between the overrunning clutch teeth Il, I8. This 'causes more torque to be transmitted from the pinion vto the control nut 'I so as to acceleratethe demeshing movement of the parts. v

In Fig. `5 the function accomplished vby the spring 34 and its associated parts in Fig."4 isperformed by a spring member 3B in the form of a slotted sleeve -xed in any suitable manner in the end of the screw shaft 4 as shown'at '31 and having a plurality of projections 38,'po`sitioned to engage flange 35 of the coupling member shortly before the disengagement of thev pinion-from the engine gear. The vI e'si'stance thus encountered bythe coupling member causes the overrunning clutch teeth I'I, I8 to be'pressed vtogether so as to accelerate -the demes'hing 'action as described above. In addition to this function, the `sleeve 36 lalso cooperates v'with the flange 35 lto constitute means for preventing lt-he parts Vfrom drifting laway from idle position due'to vibration or other causes.

Although certain structure has been shown and described in detail, it rwill be understood that other embodiments are vpossible and that changes vmay Ab'e made in thedesi'gn'and arrangement of the parts without departing from the spirit of the invention.

1. In an engine starter drive a power shaft,'a screw shaft fixed thereon, a control nut threaded on the screw shaft, a pinion slidably journaled on the power shaft for movement into and out of mesh with agear of an` engine to Ybe started, means for actuating the pinion from the control not including an overrunning clutch and means actuated by the demeshing movement of the pinion for increasing the drag of the overrunning clutch.

2. An engine starter drive of the type set forth in lclaim l in which the overrunning clutch cornprises a pair of longitudinally movable members having lcooperating teeth and mean-s actuated Iby the Withdrawal yof the pinion from mesh for yieldingly pressing the clutch members together.

3. An engine starter drive as set forth in `claim -2 in'wh'ich the means for pressing the clutch members together is sov located Vas to become effective shortly before the pinion ismoved out of contact with the engine gear.

4. In engine starter gearing a power shaft, a pinion slidably journaled thereon for movement into and out of mesh with an engine gear, means responsive to acceleration of the power shaft for moving the pinion into mesh with the engine gear1 and then connecting the pinion to rctate with the power shaft to crank the engine, said means being effective to withdraw the pinion when it is rotated faster than the power shaft, said means including an overrunning clutch arranged to transmit a small amount of torque from the pinion to the traversing means while overrunning to initiate slow withdrawal of the pinion from mesh, and means actuated by said withdrawing movement shortly before the pinion disengages from the engine gear', for augmenting the torque transmitted from the inion while overrunning so as to accelerate the final demeshing movement of the pinion.

5. Engine starter gearing as set forth in claim 4 in which the torque augmenting means comprises a yielding abutment engaged by the driv ing overrunning clutch member and thereby causing the overrunning clutch members to be pressed together.

6, Engine starter gearing as set forth in claim 5 in which the driving overrunning clutch member disengages from said abutment when the Jinion moves out of contact with the engine gear.

7. in an engine starter drive a power shaft, a pinion slidably jcurnalled thereon for movement into and out of mesh with a gear of an engine to be started, a screw shaft fixed on the power shaft, a control nut threaded on the screw shaft, a coupling member transmitting torque from the control nut to the pinion having a dental overrunning clutch connection with the pinion, said control nut and coupling member having interenga-ging coupling teeth with inclined driving surfaces, a light compression spring between the control nut and coupling member normally holding the coupling teeth partly separated and the overrunning clutch fully engaged, a heavy compression spring on the control nut, means on the control nut for holding the heavy spring under initial compression and means including said heavy spring for limiting the separation of the pinion and control nut.

8. An engine starter drive as set forth in claim l including further means on the screw shaft for positively limiting the longitudinal movement of the control nut thereon in both directions.

9. An engine starter drive as set forth in claim '7 in which the means for limiting the separation of the pinion and control nut includes a barrel member and means cooperating therewith to compress said heavy spring by the camming action of said inclined coupling teeth.

DONALD L. MULLER.

Name Date Digby Jan. 24, 1950 Number 

